Modular impactor head

ABSTRACT

A modular impactor head includes a load transfer member, a base, and a locking assembly. The base defines a space sized and configured to receive the load transfer member therein and to constrain movement of the load transfer member relative to the base in a plurality of directions. The locking assembly is sized and configured to constrain movement of the load transfer member with respect to the base in at least one direction such that the load transfer member is fixed to the base.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/111,450, filed on May 19, 2011 claiming priority to U.S. provisionalpatent application 61/350,667, filed on Jun. 2, 2010, each of which isherein incorporated by reference in its entirety.

FIELD OF DISCLOSURE

The disclosed system and method relate to impactors for implants. Morespecifically, the disclosed system and method relate to a modularimpactor head for an implant impactor.

BACKGROUND

Medical implants that are to be received within an intramedullary canalare frequently installed with the aid of tools for creating theintramedullary canal and inserting the implant within the canal. Suchinsertion tools include implant impaction instruments referred to as“impactors”.

Conventional impactors have a load transfer member fixed to a handle.Typically, the load transfer device is fixed to the handle bycross-pinning the load transfer device to an impactor head. However, theload transfer members have a high incidence of wear, which has promptedthe development of modular assemblies. These modular assembliestypically employ a set screw assembly to maintain the load transfermember coupled to the impactor head. While these modular assembliesenable the load transfer members to be replaced when worn, the set screwassemblies are highly susceptible to fatigue, which may result infailure.

Additionally, conventional impactor handles are frequently fabricatedfrom metals due to the high structural integrity and the ability tomachine and weld metals to form the desired device. However, formingimpactor handles from metals results in the impactor having considerableweight and may be difficult for less strong surgeons to manipulate.

Accordingly, an improved impactor design is desirable.

SUMMARY

A modular impactor head is provided including a load transfer member, abase, and a locking assembly. The base defines a space sized andconfigured to receive the load transfer member therein and to constrainmovement of the load transfer member relative to the base in a pluralityof directions. The locking assembly is sized and configured to constrainthe movement of the load transfer member with respect to the base in atleast one direction such that the load transfer member is fixed to thebase.

Also disclosed is a modular impactor head including a load transfermember and a base including a plurality of sidewalls. The sidewallsextend from a bottom wall of the base to define a space sized andconfigured to receive the load transfer member. At least two of thesidewalls define slots and the bottom wall defines a cavity. The slotsof the sidewalls are sized and configured to cooperate with tabsextending from the load transfer member. A locking assembly is sized andconfigured to be received within the cavity and to lock the loadtransfer member to the base.

A method is also disclosed in which a biasing member is inserted into acavity defined by a bottom wall of a body of a modular impactor head.The modular impactor head includes a plurality of sidewalls extendingfrom the bottom wall. A space is defined by the plurality of sidewallsand the bottom wall. A locking shaft is inserted into the cavity, and atab extending from a surface of a load transfer member is aligned with aslot defined by one of the sidewalls. The load transfer member isinserted into the space in a first direction such that the tab isreceived within the slot. The load transfer member is slid in a seconddirection until the locking shaft is received within a hole defined bythe load transfer member.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will bemore fully disclosed in, or rendered obvious by the following detaileddescription of the preferred embodiments of the invention, which are tobe considered together with the accompanying drawings wherein likenumbers refer to like parts and further wherein:

FIG. 1 is a partially exploded isometric view of one example of amodular implant impactor;

FIG. 2 is an exploded isometric view of a base and a locking assembly ofa modular impactor head in accordance with the modular implant impactorillustrated in FIG. 1;

FIG. 3 is an end view of the base and the locking assembly of themodular impactor head illustrated in FIG. 2 when assembled;

FIG. 4 is a top side view of a load transfer member in accordance withthe modular implant impactor illustrated in FIG. 1;

FIG. 5 is an end view of the load transfer member illustrated in FIG. 4;

FIG. 6 is a side view of the load transfer member illustrated in FIG. 4;

FIG. 7 is an end view of the load transfer member illustrated in FIG. 4;

FIG. 8 is a bottom side view of the load transfer member illustrated inFIG. 4;

FIG. 9 is a partially exploded cross-sectional view of the modularimpactor head illustrated in FIG. 2;

FIG. 10 is a cross-sectional view of the modular impactor headillustrated in FIG. 2 during assembly;

FIG. 11 is a cross-sectional view of the modular impactor headillustrated in FIG. 2 after assembly;

FIG. 12 is an exploded isometric view of a modular impactor handle inaccordance with FIG. 1;

FIG. 13 is a cross-sectional view of the modular impactor handleillustrated in FIG. 12 during assembly;

FIG. 14 is a cross-section view of the modular impactor handleillustrated in FIG. 12 at another stage of assembly;

FIG. 15 is a cross-sectional view of the modular impactor handleillustrated in FIG. 12 at another stage of assembly; and

FIG. 16 is a cross-sectional view of the assembled modular impactorhandle.

DETAILED DESCRIPTION

This description of preferred embodiments is intended to be read inconnection with the accompanying drawings, which are to be consideredpart of the entire written description. The drawing figures are notnecessarily to scale and certain features of the invention may be shownexaggerated in scale or in somewhat schematic form in the interest ofclarity and conciseness. In the description, relative terms such as“horizontal,” “vertical,” “up,” “down,” “top,” and “bottom” as well asderivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,”etc.) should be construed to refer to the orientation as then describedor as shown in the drawing figure under discussion. These relative termsare for convenience of description and normally are not intended torequire a particular orientation. Terms including “inwardly” versus“outwardly,” “longitudinal” versus “lateral,” and the like are to beinterpreted relative to one another or relative to an axis ofelongation, or an axis or center of rotation, as appropriate. Termsconcerning attachments, coupling, and the like, such as “connected” and“interconnected,” refer to a relationship wherein structures are securedor attached to one another either directly or indirectly throughintervening structures, as well as both movable or rigid attachments orrelationships, unless expressly described otherwise. The term“operatively connected” is such an attachment, coupling or connectionthat allows the pertinent structures to operate as intended by virtue ofthat relationship.

FIG. 1 illustrates one example of an improved impactor 100. As shown inFIG. 1, impactor 100 includes an impactor head assembly 102 that may bereleaseably coupled to a handle assembly 104. Impactor head assembly 102includes a base 106 that may be releasably coupled to a load transfermember 108. A coupling member 110 extends from a proximal portion 112 ofbase 106 of impactor head 102 for coupling to handle 104.

As best seen in FIGS. 2 and 3, a plurality of sidewalls 114, 116, 118,and 120 extend in a distal direction from base 106, which has asubstantially rectangular shape. Lengthwise sidewalls 114 and 116 eachdefine a slot 122 extending from a distal edge 124 to a bottom wall 126where a width of the slot increases to form tabs 128 as shown in FIG. 3.One or both of lengthwise sidewalls 114, 116 may include an alignmentfeature 130 in the form of a notch, scribe line, dimple, or otherdiscernable indicia located at an approximate mid-point of the length.Sidewall 114 defines one or more holes 132 that extend through sidewall114 and communicate with depressions 134 disposed on either side ofcavity 136 in bottom wall 126 as best seen in FIG. 2. Sidewalls 114 and116 also define a through hole 138.

Sidewall 118 includes a slot 140 disposed approximately at the midpointbetween sidewall 114 and sidewall 116. In some embodiments, slot 140extends from distal edge 124 to bottom wall 126. Still referring to FIG.2, sidewall 120 defines an aperture 142 having a rectangular shape,although one skilled in the art will understand that aperture 142 mayhave other shapes including, but not limited to, oval, round,triangular, pentagonal, and hexagonal, to name a few.

As best seen in FIGS. 1 and 2, coupling member 110 extends fromrectangular base 106 in a proximal direction, i.e., in an oppositedirection with respect to the direction in which sidewalls 114-120extend. Coupling member 110 may have a body 144 with a circularcross-sectional geometry and include a reduced diameter area 146disposed along its length and a rounded taper at one end. As best seenin FIGS. 1 and 9-11, shoulder 148 may have a cross-sectional geometrythat prevents rotation. For example, shoulder 148 may have arectangular, pentagonal, hexagonal, or other cross-sectional geometry.In some embodiments, shoulder 148 has a round cross-sectional geometryincluding one or more flats for preventing rotation of impactor head 102with respect to impactor handle 104 as described below.

FIGS. 4-8 illustrate various views of load transfer member 108, which ispreferably fabricated from a polymer material in order to prevent damageto an implant. As shown in FIGS. 4-8, load transfer member 108 has asubstantially rectangular impact surface 150 with sidewalls 152, 154,156, and 158 extending therefrom. Sidewall 152 includes a protrusion 160extending from rectangular impact surface and being sized and configuredto be received within slot 140 defined by sidewall 118 of base 106 asbest seen in FIGS. 5 and 8. FIGS. 7 and 8 illustrate rectangular detent162 extending from sidewall 154 that is sized and configured to bereceived in aperture 142 defined by sidewall 120 of base 106. Sidewalls156 and 158 may have an identical structure including channel 164 and acutout 166, which defines a tab 168 as best seen in FIGS. 1 and 6. Insome embodiments, sidewall 154 may be cylindrical or have anothergeometry and be configured to constrain load transfer member 108 inmultiple degrees of freedom as will be understood by one skilled in theart. Bottom surface of load transfer member 108 defines a hole 170. Insome embodiments, hole 170 is a blind hole. In other embodiments, hole170 extends through load transfer member 108 and includes a reduceddiameter section 170 a in order to permit access to a locking mechanismfor disassembling impactor head 102 as described below.

Referring again to FIG. 2, impactor head assembly 102 includes a springor biasing member 172, a pin 174, and a locking shaft 176. Biasingmember 172 is selected to have a diameter sized and configured to bereceived within cavity 136 in base 106. Pin 174 has a diameter such thatit may be press fit within through hole 138 defined by sidewalls 114 and116. Locking shaft 176 has an elongate body 178 with a circularcross-sectional geometry that is sized and configured to be receivedwithin cavity 136. Elongate body 178 defines a slot 180 having a widththat is sufficiently sized to receive pin 174 therein. One or more flats182 may be formed on opposing sides of elongate body 178 such that slot180 extends through flats 182 as best seen in FIG. 2.

To assemble impactor head assembly 102, biasing member 172 is insertedinto cavity 136 defined by base 106 as illustrated in FIGS. 2 and 9.Locking shaft 176 is then inserted into cavity 136 compressing biasingmember 172 (FIGS. 3 and 9). The one or more flats 182 may be used toalign slot 180 of locking shaft 176 with through hole 138 in base 106.With locking shaft 176 disposed within cavity 136, pin 174 is insertedinto cavity 136. Locking shaft 176 may be depressed such that end 184 isapproximately even with bottom wall 126 of base 106 in order to enablepin 174 to be received within slot 180 of locking shaft 176.

Load transfer member 108 is then loaded into the space 186 defined bysidewalls 114-120 of base 106 by aligning rectangular protrusion 160 ofload transfer member 108 with slot 140 defined by sidewall 118 of base106 and aligning tabs 168 of load transfer member 108 with slots 122defined by sidewalls 114 and 116 of base 106. As load transfer member108 is slid into engagement with base 106 as shown in FIGS. 9 and 10,the bottom wall 188 may contact end 184 of locking shaft 176 causinglocking shaft 176 to be completely disposed within cavity 136.

Load transfer member 108, which may also include an alignment feature190 in the form of a notch, scribe line, dimple, or other discernableindicia located approximately at a mid-point of the length, is slidrelative to base 106 until alignment feature 190 is aligned withalignment feature 130 at which point detent 162 of load transfer member108 is received within aperture 142 defined by sidewall 120 and tabs 128of base 106 engage tabs 168 of load transfer member 108.

When the alignment features 130 and 190 are aligned, base 106 limits allbut one degree of movement of load transfer member 108 as sidewalls 114,116, and 120 and bottom wall 126 prevent rotation, movement towards base106, and lateral movement in all directions except for one, i.e.,movement towards sidewall 118. Additionally, tabs 128 and aperture 142of base 106 prevent movement of load transfer member 108 away from base106. Thus, the only direction in which load transfer member 108 may movewith respect to base 106 when alignment features 130 and 190 are alignedis towards sidewall 118. However, the locking mechanism provided bybiasing member 172, pin 174, and locking shaft 178 constrains themovement of load transfer member 108 from being slid in the direction ofsidewall 118 such that load transfer member 108 is fixed to base 106.The locking mechanism engages load transfer member 108 by biasing member172 forcing locking shaft 178 into hole 170 defined by the bottomsurface 188 of load transfer member 108 as best seen in FIG. 11.

Impactor head 102 may be sterilized using an autoclave or other deviceeither before or after being assembled as will be understood by oneskilled in the art. Slots 122 of base 106, channel 164 of load transfermember 108, and holes 132 and depressions 134 defined by base 106communicate with each other to provide a conduit for fluid to exit themodular impactor head 102.

FIG. 12 illustrates handle assembly 104, which includes a handle body192 defining an opening 194 at one end 196. Opening 194 has an internaldiameter that is sufficiently large so as to receive coupling member 110of impactor head assembly 102. In some embodiments, opening 194 mayextend through handle body 192 to facilitate drying of handle 192 aftersterilization. Opening 194 also includes an anti-rotation feature 198,which complements the geometry of shoulder 148 of coupling member 110.For example, anti-rotation feature 198 may be an internal hexagonalgeometry as shown in FIGS. 12-14, a single flat disposed on the interiorof opening 196, or any other geometry or feature for preventing rotationof impactor head assembly 102 with respect to handle assembly 104.Opening 194 may also include an internal shoulder 200 disposed adjacentto anti-rotation feature as best seen in FIG. 13.

End 196 of body 192 defines a hole 202 adjacent to opening 194 asillustrated in FIG. 12. Hole 202 communicates with slot 204 formed alongthe length of body 192 and includes a first portion 202 a disposed onone side of slot 204 and a second portion 202 b disposed on the otherside of slot 204. Slot 204 has an oblong or rectangular shape that issized and configured to receive locking button 208 and to intersectopening 194 and hole 202. As best seen in FIGS. 13 and 14, a cavity 206is disposed at the bottom 210 of slot 204.

Locking button 208 has a rectangular shape with a cross-sectionalgeometry that is complementary to the geometry of slot 204 withsubstantially flat front and back surfaces 212 and 214. An aperture 216is formed through locking button 208 and includes a locking bar 218along its inner surface 220 as best seen in FIGS. 13 and 14, which maybe in the form of a reduced diameter area or a raised surface extendingalong an interior of aperture 216. A groove 222 may be formed through,or in the back surface 214 of, locking button 208. If groove 222 isformed through locking button 208, then it may include an area 224having a reduced size as best seen in FIGS. 13 and 14. Upper surface 226of locking button 208 may be textured or include a frictional feature228 to facilitate manipulation by a user.

To assemble handle 104, a retaining pin biasing member 230, which may bea coil spring or other device for biasing or otherwise applying a forceon a retaining pin 232, is inserted into hole 202. A locking bar biasingmember 234 is inserted into slot 204 until it is received in cavity 206as best seen in FIG. 13. Locking button 208 is inserted into slot 204until aperture 216 aligns with hole 202 at which point retaining pin 232is inserted into hole 202 a and received in hole 202 b as illustrated inFIGS. 14 and 15. The locking bar retaining mechanism comprisingretaining pin biasing member 230 and retaining pin 232 are compressedinto hole 202 b by inserting a thin elongate rod into hole 202 to forceretaining pin 232 into pin biasing member 230 until retaining pin 232 isdisposed within hole 202 b to enable locking button 208 to be furtherreceived in slot 204 as shown in FIG. 15.

As locking button 208 is further received in slot 204, groove 222,defined by locking button 208, aligns with hole 202 b resulting inretaining pin 232 being received within groove 222 as retaining pinbiasing member 230 applies a force on retaining pin 232 toward groove222. Area 224 engages retaining pin 232 to maintain retaining pin 232and retaining pin biasing member 230 within hole 202 b as best seen inFIG. 16. With retaining pin 232 received within groove 222, lockingbutton 208 is retained within slot 204, but may slide within slot 204 adistance defined by a length of groove 222.

Impactor 100 is assembled by coupling impactor head assembly 102 tohandle 104 by inserting coupling member 110 of impactor head 102 intoopening 194 of handle 104. As coupling member 110 slides into opening194, body 144 of coupling member 110 contacts locking bar 218 of lockingbutton 208, which results in locking button 208 being received moredeeply within slot 204 until aperture 216 of locking button 208 alignswith opening 194. Locking bar biasing member 234 compresses from theforce applied by locking button 208. When reduced diameter area 146 ofcoupling member 110 aligns with locking bar 218, which occurs whenanti-rotation feature 198 of opening 194 aligns with correspondinggeometry of shoulder 148, locking bar biasing member 234 forces lockingbar 208 into engagement with reduced diameter area 146.

The engagement between reduced diameter area 146 and locking bar 208prevents axial movement of impactor head assembly 102 along an axisdefined by opening 194 with respect to handle 104 to maintain impactorhead assembly 102 coupled to handle 104. The engagement between shoulder148 of impactor head assembly 102 and anti-rotation feature 198 ofhandle 104 prevents rotational movement by impactor head 102 withrespect to handle 104.

Once assembled, impactor 100 may be used as any implant impactor aswould be understood by one skilled in the art. Impactor head 102 may bedisconnected from handle 104 by applying a downward force on lockingbutton 208, which forces locking button 208 deeper into slot 204, untilaperture 216 aligns with opening 194 and then axially pulling impactorhead 102 away from handle 104.

Load transfer member 108 may advantageously be replaced if it becomesworn. To remove load transfer member 108 from base 106, a thin rod (notshown) may be used through hole 170 to remove pin 174 from itsengagement with slot 180 of locking shaft 176. With pin 174 disengagedfrom locking shaft 176, the thin rod may be inserted into hole 170 inload transfer member 108 to contact the end 184 of elongate body 178 andcompress biasing member 172 until end 184 is disposed within cavity 136.With locking shaft 176 disposed within cavity 136, load transfer member108 may be slid in the direction of sidewall 118 until detent 162 isdisengaged from aperture 142 defined by sidewall 120 and tabs 168 ofload transfer member 108 are disengaged from tabs 128 of body 106. Loadtransfer member 108 may then be removed from body 106 and replaced withanother load transfer member 108 in accordance with the assembly processdescribed above.

The modular impactor 100 described above may advantageously be fullydisassembled and assembled while providing a more rugged and robuststructure compared to conventional impactors that rely on set screwassemblies. Additionally, handle assembly 104, and more particularlyhandle body 192, may be advantageously machined or molded from carbonreinforced plastic, which enables the weight of impactor 100 to besignificantly reduced while retaining sufficient structural integrity,as the impactor handle assembly 104 does not require welding to joindifferent parts together. However, one skilled in the art willunderstand that handle body 192 may be fabricated from other materialssuch as, for example, metals and polymers.

Although the invention has been described in terms of exemplaryembodiments, it is not limited thereto. Rather, the appended claimsshould be construed broadly, to include other variants and embodimentsof the invention, which may be made by those skilled in the art withoutdeparting from the scope and range of equivalents of the invention.

What is claimed is:
 1. A modular impactor handle, comprising: a bodydefining an opening at a first end, wherein the opening is sized andconfigured to receive a coupling member of an impactor head therein; anda locking bar sized and configured to interface with a reduced diameterarea of the coupling member, wherein the locking bar prevents axialmovement of the impactor head along an axis defined by the opening withrespect to the body.
 2. The modular impactor handle of claim 1,comprising a biasing member configured to force the locking bar intoengagement with the coupling member when the coupling member is insertedinto the opening.
 3. The modular impactor handle of claim 2, wherein thebiasing member comprises a retaining pin and a spring.
 4. The modularimpactor handle of claim 3, comprising a locking button defining anaperture, wherein the locking button is sized and configured to bereceived within a slot defined by the body, wherein the apertureinterfaces with the opening, wherein the locking bar is coupled to aninternal surface of the aperture, and wherein the biasing member appliesa force to the locking button.
 5. The modular impactor handle of claim1, wherein the opening defines an anti-rotation feature to preventrotation of the impactor head with respect to the body.
 6. The modularimpactor handle of claim 5, wherein the anti-rotation feature comprisesa geometry complimentary with respect to a shoulder of the couplingmember.
 7. The modular impactor handle of claim 6, wherein theanti-rotation feature comprises an internal hexagonal geometry.
 8. Themodular impactor handle of claim 1, wherein the opening extendslongitudinally through the body.
 9. The modular impactor handle of claim1, wherein the body comprises a carbon reinforced plastic.
 10. A modularimpactor, comprising: an impactor head, comprising: a load transfermember; a base including a plurality of sidewalls extending from abottom wall to define a space sized and configured to receive the loadtransfer member therein and to constrain movement of the load transfermember relative to the base in a plurality of directions, and at leasttwo of the sidewalls each defining a respective slot; a locking assemblysized and configured to constrain movement of the load transfer memberwith respect to the base in at least one direction such that the loadtransfer member is fixed to the base; and a coupling member coupled tothe bottom wall and extending in an opposite direction with respect to adirection in which the sidewalls extend, wherein the coupling membercomprises a reduced diameter area; and an impactor handle, comprising: ahandle body defining an opening at a first end, the opening sized andconfigured to receive the coupling member of the impactor head therein;and a locking button sized and configured to be received within theslot, wherein the locking button defines an aperture configured tointerface with the opening defined by the body; a locking bar coupled toan inner surface of the aperture, the locking bar sized and configuredto interface with the reduced diameter area of the coupling member,wherein the locking bar prevents axial movement of the impactor headalong an axis defined by the opening with respect to the body.
 11. Themodular impactor of claim 10, wherein the coupling member comprises ananti-rotation feature configured to prevent rotation of the impactorhead with respect to the impactor handle.
 12. The modular impactor ofclaim 11, wherein the anti-rotation feature of the coupling membercomprises a first geometry and the opening of the impactor handledefines a second geometry, wherein the second geometry is complimentaryto the first geometry.
 13. The modular impactor of claim 12, wherein thefirst geometry comprises a hexagonal geometry and the second geometrycomprises a complimentary internal hexagonal geometry.
 14. The modularimpactor of claim 10, wherein the impactor handle comprises a biasingmember configured to bias the locking button to force the locking barinto engagement with the reduced diameter area of the coupling memberwhen the coupling member is inserted into the opening.
 15. The modularimpactor of claim 10, wherein the handle body comprises a carbonreinforced plastic.
 16. A modular impactor handle, comprising: a bodydefining an opening at a first end, wherein the opening is sized andconfigured to receive a coupling member of an impactor head therein, andwherein the body defines a slot; a locking button sized and configuredto be received within the slot, wherein the locking button defines anaperture configured to interface with the opening defined by the body; alocking bar coupled to an inner surface of the aperture, the locking barsized and configured to interface with a reduced diameter area of thecoupling member, wherein the locking bar prevents axial movement of theimpactor head along an axis defined by the opening with respect to thebody.
 17. The modular impactor handle of claim 16, comprising a biasingmember configured to bias the locking button to force the locking barinto engagement with the reduced diameter area of the coupling memberwhen the coupling member is inserted into the opening.
 18. The modularimpactor handle of claim 16, wherein the opening defines ananti-rotation feature configured to prevent rotation of the impactorhead with respect to the handle.
 19. The modular impactor handle ofclaim 18, wherein the anti-rotation feature comprises a complimentarygeometry with respect to a shoulder of the coupling member
 20. Themodular impactor handle of claim 19, wherein the anti-rotation featurecomprises an internal hexagonal geometry.